Amy Bell, who runs Amy Bell Compliance and chairs the Law Society’s money laundering task force, said the new regulations repeal and replace the 2007 version and are 118 pages long.

“Whilst much of the 2007 regulations remain intact, there are some considerable amendments and additions which will take firms some time to consider and implement,” she said.

In a statement on Friday, the Treasury said the regulations would “improve the quality” of checks done on the source of money.

“They ensure that businesses can spot suspicious activity and report it, enabling the police to act swiftly and decisively to prevent corruption or terrorist attacks.”

Legal bodies have not yet published guidance on the new regulations, in light of the government’s decision that in future there can only be only one Treasury-approved piece of AML guidance per sector.

This means the sign-off process now requires the agreement of 11 legal sector regulatory and representative bodies across the UK.

The SRA said: “We expect law firms to comply with their legal obligations and are urging law firms to familiarise themselves with the new regulations as soon as possible, and take action to comply.”

In a statement, the Law Society said: “While we had hoped to have had the guidance approved and published ahead of the commencement of the new regulations, this has unfortunately not been possible…

“We recognise that many of the changes required under the new regulations will mean significant changes to firms’ systems and controls.”

It said the Legal Sector Affinity Group – a group representing the legal sector AML supervisory bodies to government, including the Law Society and SRA – has told the Treasury that “a sensible supervisory approach towards the new regulations would be to give firms and individuals a period of time to adjust to their new obligations.

“The group feels this is particularly important given the extremely short timeframe between when supervisors and those they supervise will see the final version of the MLRs and when those MLRs come into force.”

Ms Bell said a central theme of the regulations was firms needed to take a risk-based approach, meaning they need to complete a risk assessment of their practices and review their AML policies.

There were a number of practical changes firms were likely to need to make to their customer due diligence process, she said, such as expanding the list of information obtained on a corporate client to include information about its constitution, possible from review of the articles of association.

“This could add considerable time to the process,” Ms Bell said.

Another issue was a wider definition of beneficial owners, while the definition of a politically exposed person (PEP) now included domestic PEPs, and the definition has changed to include the governing bodies of political parties, and the boards of international organisations.